Environmental and Acceptance-Based Innovations for Weight Loss Maintenance Obesity is a serious and prevalent health problem with widespread medical, psychosocial and economic consequences. Although behavior therapy (BT) is the gold standard among non-surgical approaches, weight regain usually begins shortly after treatment ends; nearly all of weight lost in these programs is regained by 5 years after treatment. Several factors appear to make weight loss maintenance challenging including the obesogenic food environment, the rewarding value of food, and labor-saving devices and a built environment that reduce energy expenditure. One promising way of improving BT programs is to teach participants how to modify their personal food and physical activity environment so that it provides maximal support for desirable weight control behaviors. Intervention components can include modifying the type, nutritional composition, variety, and portion size of food available at home; modifying the availability of exercise equipment and sedentary activities in the home; increasing the saliency of the consequences of eating and exercise choices; and obtaining support for environmental changes. A second innovative way of improving BT programs is to incorporate components of Acceptance and Commitment Therapy (ACT) in order to (a) bolster participants' commitment to behavior change, (b) build distress tolerance skills, and (c) promote mindful awareness of weight-related behaviors and goals. Such skills should improve long-term adherence to dietary and physical activity recommendations (and therefore weight loss maintenance). We expect that there will be a synergy and a complementary nature between these treatment components and the environmental treatment components. Maintaining a home environment that facilitates weight control requires commitment, distress tolerance, and awareness, because individuals must make decisions about environmental modifications and maintain these modifications. Additionally, there are limits to the home environment approach because individuals will continue to encounter many challenging situations in which they cannot modify the environment to any meaningful extent; acceptance-based skills may promote healthy choices in such challenging situations. As a test of the combined approach, participants will be randomly assigned to one of three conditions: 1)BT, 2) BT plus modifying the home environment (BT+E), or 3) BT plus modifying the home environment and training in acceptance-based skills (BT+EA). Treatment will last 1 year. Participants will be 297 overweight and obese individuals recruited from the community. Thirty percent of participants will be ethnic minorities. Assessments will be completed at baseline and Months 6, 12 (end of treatment), 18 (i.e., 6-month follow-up), and 24 (i.e., 12- month follow-up). The primary aim of the study is to test the hypothesis that participants in the BT+EA condition will maintain more weight loss than those in the BT condition at 12-month follow-up. Secondary aims will compare weight loss in BT+EA vs. BT+E, and BT+E vs. BT, and examine dietary intake and physical activity as outcomes. Exploratory aims will examine mediation and moderation of treatment outcome.